Prefatory :

As per the directions from Government, the Tamil Nadu Water Supply and Drainage Board (TWAD Board) has undertook the investigation works and preparation of Detailed Project Report (DPR) for providing Underground Sewerage Scheme for Velankanni Special grade Town panchayat in Nagapattinam District during 7/2011. Velankanni Town Panchayat is not provided with underground sewerage system. The town is provided with open drains in the main area of the town and septic tanks.

Necessity of the Scheme

The existing open drain system is not functioning satisfactorily. The water is stagnating in many places and due to that mosquitoes and flies are developed, which cause health hazards. In order to improve the hygienic conditions, underground sewerage system is a must for Velankanni Town Panchayat.

Population and Projection

In designing sewerage system for any town the important factor is the present population and its expected rate of growth. The concept of the base year 2018 is considered for projecting the intermediate population for 2033 (15 years from base year) and the ultimate population for 2048 (30 years from base year).

Design Population

Year

Population

Base year 2018

13000

Intermediate Year 2033

16000

Ultimate Year 2048

19000

Detailed Description of Proposal

The proposed UGSS Scheme is designed for the ultimate stage i.e. year 2048.

The Sewerage work is divided into the following five categories and described subsequently.

House connections and local sewerage.

Main and trunk sewers.

Pumping station.

Pumping main.

Sewage Treatment plant.

House Connection and Local Sewerage Including Branch Sewers

The total number of house service connections calculated as 2280 Nos. The Velankanni town panchayat is divided into two parts in east-west directions for UGSS purpose, the western side is termed as Zone I and the Eastern side is termed as Zone II and Zone II A.

House Service Connection Details

HSC

Zone I

Zone II & Zone II A

Total

Domestic-110 UPVC

565

1411

1976

Commercial – 160 UPVC

4

300

304

Total

569

1711

2280

Main And Trunk Sewers

The total main and trunk sewer covers a total stretch of 19918 m and total manholes of 714 Nos and 2Nos of Lift manholes.

Sewer line Details

S.No

Size of Pipe

Zone I

Zone II

Zone II A

1

160 mm UPVC

1295 m

2

200 mm UPVC

6389 m

10195 m

313 m

3

250 mm UPVC

104 m

380 m

4

200 mm RCC

57 m

750 m

5

350 mm RCC

318 m

6

400 mm RCC

57 m

60 m

Details of Manholes

S.No

Type of Manhole

Zone I

Zone II

Zone II A

Total

1

Rectangular Brick Manhole

165

289

15

469

2

Circular RCC Manhole (Up to 2.5 m)

68

30

--

98

3

Circular RCC Manhole (Beyond 2.5 m)

46

100

1

147

TOTAL

279

419

16

714

Pumping Station

The sewage generated from the Zone I is collected at Pumping Station I and is proposed to be pumped to STP. The sewage generated from the Zone II and Zone II A is collected at Pumping Station II and is proposed to be pumped to STP. The capacity of collection well has been determined in such a way that for any combination of inflow and pumping, the cycle of operation for each pump will not be less than 5 minutes and maximum detention time will not exceed 30 minutes. Pumping quantity is 0.5mld for zone I and 1.45 mld for zone II for intermediate and 0.56 & 1.47 mld respectively for ultimate.

Pumping Main

The pumping main carries flow from the proposed pumping station (2 Nos) to the STP.

Zone I Pumping Station to STP – 150 mm CI Pipes – 260 m

Zone II Pumping Station to STP – 250 mm CI Pipes – 2416 m

Zone II A to Zone II – 150 mm CI Pipes – 30 m

Sewage Treatment Plant

It is necessary to provide complete biological treatment of sewage before disposal into a water way. The type of treatment is generally decided based on the effluent standards prescribed by the regulatory agencies, such as Central Pollution Control Board, Tamil Nadu Pollution Control Board.

Considering the available skills and the fact that, the sewage treatment is going to be a new area of activity for the local body to handle, Extended aeration method is proposed for this Scheme.

Details of Sewage Treatment Plant

Capacity of STP : 2.33 MLD

Technology : EASP Technology

Extent allocated : 0.67 Acre

Area Required :0.6 Acre

Final Disposal : Reuse after let into ULB Pond (Kazhugukulam)

Disposal Arrangements: To be conveyed by 350 mm RCC pipes

Cost of the Scheme

The total cost of the scheme works out to Rs. 33.51 Crores for installation and Rs. 24.65 Lakhs for annual maintenance.

Mode of Finance

The Scheme is under implementation with funding from Government of india 50%- Rs11.66 Crores,Government of Tamil Nadu- Rs 4.66 Crores,Urban Local Body-Rs 7.00 Crores and IUDM Share of Rs10.19 Crores.

Maintenance

On completion, the scheme will be maintained by the Contractor for the period of 5 Years and after that the Scheme will be maintained by Town Panchayat.

Present Stage:

The work order for the scheme has been issued on 02.01.2017 and work commenced on 27.01.2017. So far, 53% of work has been completed and expenditure incurred is Rs. 13.55 Cr.(48%) .